The BNP organised special prayer sessions after Jummah prayers across the country on Friday seeking speedy recovery of the party's chairperson Khaleda Zia.
In the capital, the programme was held by the political party in the south premises of Baitul Mukarram National Mosque.
BNP standing committee member Khandaker Mosharraf Hossain, who was the chief guest at the prayer function, said, "We are praying to Allah for the recovery of our leader in mosques and other religious institutions across the country."
There is no legal obstacle for Khaleda to go abroad for advanced medical treatment but the government is not allowing her to go without showing any valid reason, added the BNP leader.
"Her [Khaleda] physical condition is very critical and gradually deteriorating. At present, there is no other treatment for her in the country. So we are asking the government for arranging her treatment abroad," said Mosharraf Hossain.
However, the government says she cannot leave Bangladesh as per the conditions of the temporary release from jail.
Among others, BNP standing committee member Nazrul Islam Khan, Mirza Abbas, Dhaka city unit BNP convener Aman Ullah Aman and member secretary Aminul Haque were also present on the occasion.
Earlier on Wednesday, the BNP announced an 8-day programme from 25 November to 4 December demanding their party chief Khaleda Zia's release and treatment abroad.
Dr AZM Zahid Hossain, a personal physician of the former prime minister and member of the medical board formed for Khaleda Zia's treatment, told BBC Bangla that she was chronically ill with arthritis, diabetes, kidney and heart problems.
At present, her liver problem has become complicated and that is why the medicine for other diseases is not working properly.
"'Chronic liver disease has reached such a critical stage that sometimes she has some GI bleeding (bleeding in the stomach)," said Dr Zahid Hossain.
He further said that an operation on the liver has become an emergency but there are no modern facilities for such an operation in Bangladesh.
For the last few days, BNP leaders and activists across the country have been staging protests to press home their demands and have had clashed with law enforcers at different places across the country.
BNP lawmakers had earlier threatened to step down if their party leader was not allowed to go abroad.
The BNP chief landed in jail in February 2018 in the Zia Orphanage Trust corruption case. On 30 October that year, the High Court extended her punishment to 10 years dismissing her appeal.
Following the outbreak of Covid-19, the government on 25 March last year granted her temporary release on conditions at the request of her family. Till now, the term of her release has been extended four times.
She is still facing at least 36 ongoing cases.